The purpose of this project is to compare levels of dopamine (DA) transporters in subjects with cocaine dependence to that of normal subjects. This will be done using the novel ligand {123I} methyl 3B-(4- iodophenyl) tropane-2-Bcarboxylate ({123I}B-CIT or B-CIT and single photon emission computed tomography (SPECT). We studied 25 cocaine addicts and 24 healthy controls. This cohort was matched on a group basis for age and gender. The data collected provide strong in vivo evidence for post- mortem findings of increased striatal DAT in the brains of cocaine abusers. We plan to continue this study.